1. Field of the Invention
The present invention relates to a control apparatus for controlling a semiconductor chip such as an LED array used as a recording light-emitting element, moreover to an image recording apparatus for forming a visible image on a recording medium through an electrophotographic recording system by using the semiconductor chip.
2. Related Background Art
A self-scanning LED array (hereafter referred to as SLED) has been used so far as a recording light-emitting element.
The self-scanning LED array is disclosed in Japanese Patent Application Laid-Open Nos. 1-238962, 2-208067, 2-212170, 3-20457, 3-194978, 4-5872, 4-23367, 4-296579, and 5-84971, JAPAN HARD COPY, proposal of optical-printer light-emitting array constituted by integrating 91 (A-17) driving circuit, and proposal of self-scanning light-emitting element (SLED) using the PNPN thyristor structure of IEICE (Institute of Electronics, Information and Communication Engineers), Mar. 5, 1990, and noticed as a recording light-emitting element. The configuration of an SLED array head will be described below.
FIG. 8 shows a schematic configuration of the SLED array head.
Symbol 211 denotes an SLED semiconductor chip. Symbol 212 denotes a base substrate for mounting the SLED semiconductor chip 211, which is configured by a printed circuit board made of glass epoxy or ceramic. Symbol 214 denotes a driver IC for receiving a control signal from an external unit to generate a driving signal for the SLED semiconductor chip 211.
Symbol 215 denotes a bonding wire for connecting output signals supplied from the driver IC 214 (xcfx861, xcfx862, xcfx86S, and xcfx86I) and a negative-electrode-side power-supply input (GND as for this embodiment) to the SLED semiconductor chip 211 respectively. Symbol 216 denotes a positive-electrode (+) power-supply pattern extended to the base substrate 212 (+5V as for this embodiment). Symbol 217 denotes silver paste for electrically connecting and bonding the positive-electrode-side power-supply pattern 216 extended to the base substrate 212 with the back-face electrode of the SLED semiconductor chip 211 to fix them.
The SLED semiconductor chip 211 frequently uses a method of using the substrate of a chip as an anode because anodes of a light-emission thyristor and a transfer thyristor both serve as a common line and thereby, serve a maximum operating-current route and due to electrical characteristics of P and N of a semiconductor (generally, GaAs semiconductor is used) and problems on fabrication process.
When using a method of using the substrate of a semiconductor chip as a power-supply input unit and connecting the back-face electrode of the semiconductor chip with the power-supply pattern of a base substrate by a conductive adhesive and fixing them, it is inevitable to use a material containing positive (+) metal ions (e.g. silver paste) in order to select a low-resistance material of a predetermined level as the conductive adhesive.
As for the SLED semiconductor chip 211 described above, however, a substrate normally serves as a positive electrode. The substrate is electrically connected with the power-supply pattern 216 of the base substrate 212 by the silver paste 217 through a back-face electrode or the like.
Therefore, an electric-field configuration is formed in which positive ions in the substrate-side silver paste 217 (conductive adhesive) are attracted to the epitaxial-layer side through a chip-side face or the like at a portion serving as a negative electrode in the signal input unit of the epitaxial-layer-side face of the SLED semiconductor chip 211 configuring as a circuit opposite to the substrate-side face of the SLED semiconductor chip 211. The distance between the signal input unit on the epitaxial-layer-side face and the silver paste 217 at the substrate side is approximately 600 xcexcm.
The attracted positive ions are deposited through reaction with other impurity ions. Therefore, if the deposition reaction continuously occurs, a short circuit is formed between the epitaxial-layer and the substrate due to reasonable elapse of time and thereby, the original operation of an SLED can not be performed.
Therefore, it is an object of the present invention to provide a high-reliability driving controller and image recording apparatus capable of preventing the probability of short circuits formed between electrodes.
It is an object of the present invention to solve the above problems.
That is, the present invention provides a control apparatus for controlling a semiconductor chip provided with an electrode on its back face and other faces and having a recording element to drive the recording element by connecting the electrode on the back face of the semiconductor chip to a base substrate by a conductive adhesive and inputting a power supply and a control signal to the semiconductor chip from the electrodes on the back face and other faces of the semiconductor chip, which comprises means for controlling portions between the electrode on the back face and the electrodes on the other faces of the semiconductor chip to a high impedance or the same potential in a predetermined period in which the recording element is not driven.
Moreover, the present invention provides a control apparatus for controlling a semiconductor chip provided with an electrode on its back face and other faces by connecting the electrode on the back face of the semiconductor chip to a base substrate by a conductive adhesive and inputting a power supply and a control signal to the semiconductor chip from the electrodes on the back face and other faces of the semiconductor chip, which comprises means for setting portions between the electrode on the back face and the electrodes on the other faces of the semiconductor chip to a high impedance or the same potential in a predetermined period in which the semiconductor chip is not driven.
Furthermore, the present invention provides an image recording apparatus for controlling a semiconductor chip provided with an electrode on its back face and other faces and having a recording element and recording an image on a recording medium to drive the recording element by connecting the electrode on the back face of the semiconductor chip to a base substrate by a conductive adhesive and inputting a power supply and a control signal to the semiconductor chip from the electrodes on the back face and other faces of the semiconductor chip, which comprises means for controlling portions between the electrode on the back face and the electrodes on the other faces of the semiconductor chip to a high impedance or the same potential in a predetermined period in which the recording element is not driven.
Furthermore, the present invention provides a control method for controlling a semiconductor chip provided with an electrode on its back face and other faces and having a recording element to drive the recording element by connecting the electrode on the back face of the semiconductor chip to a base substrate by a conductive adhesive and inputting a power supply and a control signal to the semiconductor chip from the electrodes on the back face and other faces of the semiconductor chip, which comprises the step of controlling portions between the electrode on the back face and the electrodes on the other faces of the semiconductor chip to a high impedance or the same potential in a predetermined period in which the recording element is not driven.
Furthermore, the present invention provides a control method for controlling a semiconductor chip provided with an electrode on its back face and other faces by connecting the electrode on the back face of the semiconductor chip to a base substrate by a conductive adhesive and inputting a power supply and a control signal to the semiconductor chip from the electrodes on the back face and other faces of the semiconductor chip, which comprises the step of setting portions between the electrode on the back face and the electrodes on the other faces of the semiconductor chip to a high impedance or the same potential in a predetermined period in which the semiconductor chip is not driven.
Furthermore, the present invention provides an image recording apparatus control method for controlling a semiconductor chip provided with an electrode on its back face and other faces and having a recording element and recording an image on a recording medium to drive the recording element by connecting the electrode on the back face of the semiconductor chip to a base substrate by a conductive adhesive and inputting a power supply and a control signal to the semiconductor chip from the electrodes on the back face and other faces of the semiconductor chip, which comprises the step of controlling portions between the electrode on the back face and the electrodes on the other faces of the semiconductor chip to a high impedance or the same potential in a predetermined period in which the recording element is not driven.
Other objects, configurations, and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.